Improvement in bridges



e'rnNr 1 FIG-F.

HENRY PETTIT, or PHILADELPHIA, PENNSYLVANIA, A ssIeNon or @Nn- HALF' His RIGHT To JOSEPH M. wILsoN, orvsAME PLAGE.

f IMPROVEMENT IN BRIDGES.

Specification forming part o'f Letters Patent No. 136,177, dated February 25, 1873.

To all whom it may concern:

Beit known that I, HENRY Perrin?, of the city and county of Philadelphia, in the State of Pennsylvania, have invented a new and useful Improvement in Bridges; and I do hereby declare the following to be a full, clear, and exact decription thereof, which will enable others skilled in the art to which it appertains to make and use the said improvement, reference being had to the accompanying drawing, which forms a part of this specification, and in which- Figures 1 and 3 are vertical sections of two several forms of the said improvement taken in the direction of the length of the bridge. Figs. 2 and 4 are elevations corresponding to Figs. 1 and 3, respectively, and takentrans` versely to the length of the bridge; and Figs.

` 5 and 6 are crosssections of modifications of the flanged cross-girder.

The same parts are'denoted by thel same letters in all the figures.

The object of this invention is to prevent the unequal distribution of strain among the several links composing a chord, which frequently occurs where such links support beams or girders of considerable length, as in the case of door-beams resting on the lower chord-links of an iron trussbridge. When such beam or girder is subjected to the strain caused by a rolling load its middle portion will be more or less deected downward and its extremities correspondingly raised, thereby tending to throw the entire weight of the load upon the inner links on each side. Another cause tending to the same effect is, that the upper edges of the supporting-links are frequently not in the same horizontal plane, so that, even when not loaded, the beam does not rest evenly up.- on them all.

In order to secure the equal distribution of the weight among the several links on each side, I have devised the following improvement, which consists of a iiauged cross-girder resting on said links, and also' of a blockcombined with said girder, which devices arie'constructed and arranged as hereinafter described.

A A in the drawing represent the links which form the lower chord of a bridge-truss, apart only of the length of the link. being shown in Figs. l and 3. B is the danged cross-girder, consisting of a pieceof :i3-beam placed on its side so that the lower flanges shall rest on thelinks. C is a block, which rests on the web and between the upper ilanges of beam B. The lower surface of C is made to t the side of B exactly, and its upper surface is beveled (or it may be curved) downward from the middle toward each end, as shown in dotted lines in Fig. 2. Upon the top a a of the beveled block, as shown in Figs. l and 2, rests one end' of the floor-beam D, Whose other end rests in like manner on a block supported by a flanged cross-girder and links on the other side ofthe bridge, which, being all precisely like those already shown, are not represented in the draw- A ing.

To prevent vlateral movement of the floorbeam the blocks G may be made with a central longitudinal groove wide enough to receive the bottom of said beam, which rests between the lips on either side, as shown in Fig. 1. When the beam D is subjected to a load its extremity outside of the line of sup port a. a, Figs. l and 2, is elevated,land the part between its center and said line of support is depressed, the beveled or curved sur face of block C permitting the free deiection of the beam. The block C must be of sufficient height and length to prevent the floorbeam from coming into contact with the crossgirder when deflected. I prefer to make the cross-girder of rolled iron, `and the block C of cast-iron or cast-steel.

As already stated, the upper edges of the links A A are often not in @he same plane. The employment of the flanged girder B, however, with the edges of its ianges resting-on the links, permits this defect to be easily counteracted, enabling me to adjust the bearing of said girder evenly on all the links by clipping or slotting the anges with a chisel.

Figs. 3 and 4. represent another form of my improvement, in which the floor-beam is sus pended from the cross-girder. On the washer E, which rests on said girder, is supported the headf of the suspension-bolt F, whichl passes `through the girder and block C. The floorbeam is in this case composed of two channel. bars, G H, united by rivets and sleeves h, and rests on the plate or washer I and nut K. The block C is placed below the links, and in an inverted position, its at surface against their lower edges. It may be cast with a lug, L,

grooved or slotted to receive the links. The nut K is screwed up to bring the top of the floor-beam against the middle line of the bearing-block. When the middle of the beam G H is depressed by a load the bevel of block C will permit the end to rise freely.

Where the great weight of the floor-beams demands a greater bearing-surface than the edges of the flanges of B, I rivet to the lower side thereof a piece of T- iron, M, as shown in Fig. 5, Vso that three edges rest on the links. A still greater number of bearing-edges may be obtained by substituting for the 'J2-beam B a channel-bar, N, with two smaller channelbars, O and P, riveted thereto, as in Fig. 6.

Witnesses: HENRY PETTIT.

JOHN R. BINGAMAN, THOMAS LEE. 

